#define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
#include <math.h>
#include <stdbool.h>

bool judge(int x)
{
	if (x <= 1)
	{
		return false;
	}
	int bound = (int)sqrt(x) + 1;
	for (int i = 2; i < bound; i++)
	{
		if (x % i == 0)
		{
			return false;
		}
	}
	return true;
}
int main()
{
	int a;
	while (scanf("%d", &a) != EOF)
	{
		if (judge(a))
		{
			printf("yes\n");
		}
		else {
			printf("no\n");
		}
	}
	return 0;
}